Solve 12x + 15 = −9

The solution of 12x + 15 = −9 is x = -2.

12x + 15 = -9\ \Rightarrow\ x = -2

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The lines y = 12x + 15 and y = -9 meet at x = -2. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the addition, then the multiplication.
$12x + 15 = -9$
2
Subtract 15 from both sides:
$12x + 15 - 15 = -9 - 15 \ \Rightarrow\ 12x = -24$
3
Divide both sides by 12:
$\frac{12x}{12} = \frac{-24}{12} \ \Rightarrow\ x = -2$
4
Check: put x = -2 back into the equation.
$12\cdot(-2) + 15 = -24 + 15 = -9 \checkmark$

LaTeX source of the formulas on this page

\[ 12x + 15 = -9\ \Rightarrow\ x = -2 \]
\[ 12x + 15 = -9 \]
\[ 12x + 15 - 15 = -9 - 15 \ \Rightarrow\ 12x = -24 \]
\[ \frac{12x}{12} = \frac{-24}{12} \ \Rightarrow\ x = -2 \]
\[ 12\cdot(-2) + 15 = -24 + 15 = -9 \checkmark \]

Trying values of x in 12x + 15 = −9

x	12x + 15	Equals -9?
-4	-33	no
-3	-21	no
-2	-9	yes
-1	3	no
0	15	no

Questions

What is x in 12x + 15 = −9?

The solution of 12x + 15 = −9 is x = -2.

How do you solve 12x + 15 = −9?

Subtract 15 from both sides to get 12x = -24, then divide both sides by 12 to get x = -2.

How do I check the answer?

Replace x by -2: 12(-2) + 15 = -9, which is -9.

Solve 12x + 15 = −9

How to work it out

Trying values of x in 12x + 15 = −9

Questions

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